1. Field of the Invention
The present invention relates to a locking connector and adapter for interfacing a standard electrical plug to a receptacle. In particular, the present invention relates to an adapter having two independent, releasable locking mechanisms, the first mechanism for securing the prongs of an electrical plug therein and the second mechanism for securing the adapter to a standard receptacle.
2. Discussion of Background
Inadvertent removal of an electrical plug from a socket, outlet strip, or wall-mounted receptacle has been a matter of concern since electrical appliances became common. Almost everyone who has ever used a hand mixer, vacuum cleaner, power tool, or other hand-manipulated electrical appliance has accidentally pulled the plug out of a wall outlet. At best, such interruptions are annoying and inconvenient for the user, who has to stop work to re-insert the plug into the outlet before he can continue. In some situations, replacing the plug significantly disrupts work in progress, as when a construction worker has to climb down a ladder to replace the plug, then climb back up to resume work. Over time, repeated stress on the plug may damage the conductors to the point that the power cord must be replaced. In some situations, damaged plugs and loose connections can lead to potentially dangerous sparking and electrical shorts.
A wide variety of locking electrical adapters and connectors, for wall outlets, plugs, sockets, extension cords and the like, have been developed in response to these concerns. Many of these devices have slidable actuators and/or locking blocks for securing the prongs of an electrical plug into a wall outlet. Burkhart, Sr. provides such a device, which has a lockable, spring-loaded socket with a pair of hinged jaws for retaining an electrical plug in place (U.S. Pat. No. 5,551,884). The plug can be released from the socket by simply pushing it inwards, then allowing it to be thrust out under spring pressure.
In U.S. Pat. No. 5,108,301, Torok discloses a locking cord connector that includes a non-conductive housing, a pair of conductors each having a male and a female electrical contact (each with leaf-type springs), two spring-loaded locking mechanisms with slide blocks, and a slidable actuator. The first locking mechanism locks the male electrical contacts to a receptacle; the second locks the female contacts to another plug (such as a conventional plug of an electrical appliance). Long shows a socket with a releasable locking mechanism (U.S. Pat. No. 4,909,749). His device includes a housing that contains transversely spaced contact bars and a cam-operated clamp that locks the contact bars and the prongs of a plug together to deter removal.
Borges discloses a self-locking electrical connector consisting of a male plug and a female receptacle (U.S. Pat. No. 4,867,697). The receptacle includes a selflocking mechanism with a spring-loaded locking block which automatically locks the two parts together after insertion of the prongs of the male plug.
Strand's connector, described in U.S. Pat. No. 4,700,997, is designed for attaching a flat electrode (such as an EEG electrode) to a cable. The connector includes resilient upper and lower jaws that are joined at their respective rear ends by a flexible, resilient spring, and a slidable actuator that compresses the jaws together to hold a flat electrode in place.
Hong's device (U.S. Pat. No. 4,627,681) includes a movable wedge for pressing the male and female contacts together, whereas Imhoffs plug (U.S. Pat. No. 4,544,216) has a locking ground prong with a longitudinal "V"-shaped or "U"-shaped recess that holds a slidable, spring-loaded locking member. Warner, et al. provide a locking electric receptacle that includes a push-button rod and toggle mechanism for frictionally engaging the prongs of a male plug (U.S. Pat. No. 3,710,304).
Mangold (U.S. Pat. No. 2,436,586) and Cornwell (U.S. Pat. No. 2,261,615) provide plugs that can be laterally expanded upon insertion into a socket in order to maintain good electrical contact. Both devices include slide actuators for moving the elements that expand the prongs. Osborn's connector has a coupler with two notched tongues, teeth shaped to engage the tongues, and a transverse slidable actuator for locking it into position (U.S. Pat. No. 1,536,688).
Rotatable actuators for electrical devices are also known in the art. Torok discloses such an actuator in U.S. Pat. No. 5,197,897. His device has a non-conductive housing, a pair of conductors, two spring-loaded locking mechanisms with slide blocks, and a slidable actuator. One of the locking mechanisms locks the male electrical contacts to a receptacle; the other locks the female contacts to another plug.
Other designs include Garrison's three-prong plug with a hollow, locking ground prong (U.S. Pat. No. 5,480,318). A spring-loaded catch that engages the front wall of a socket or wall outlet is attached to the prong. The catch can be released by pushing the spring in with a nonconducting rod. Dynia's locking connector (U.S. Pat. No. 5,427,543) includes two "U"-shaped connectors for receiving the prongs of an electrical plug. A sliding cam assembly activates a spring-loaded pin to compress the sides of the connectors and retain the prongs in place. Ursich provides a self-locking female electrical socket with an automatic release mechanism and two balls that engage the holes in the prongs to secure them in place (U.S. Pat. Nos. 5,393,239 and 5,129,836). The actuator consists of a shaft with a cut-out area that permits the user to engage/disengage the balls mounted in the body of the device.
Benjamin (U.S. Pat. No. 1,660,290) shows an electrical plug and outlet combination wherein the plug is fitted with hooks and latching fingers that mechanically connect it to corresponding openings in the outlet plate. The fingers can be disengaged by a thumb screw to permit removal of the plug from the socket. Frank's self-latching electric plug has a movable arm with a lug at one end and a hook at the other end (U.S. Pat. No. 2,408,551). When the arm is in a neutral position, the plug can be inserted into (or removed from) a matching socket; after insertion, the arm is moved into a locking position where the hook latches onto a shoulder to secure the plug in place.
Dennis provides a swivel coupling lock with spring hooks that engage corresponding grooves in the prongs of an electrical plug (U.S. Pat. No. 1,404,098). Two buttons can be pushed inwards to disengage the hooks and permit removal of the plug. Chiarolanzio's snap lock extension cord and power tool connector (U.S. Pat. No. 5,069,634) positively engages a plug to an extension cord or wall outlet having two outwardly-projecting flexible fingers with locking tabs. The matching appliance plug has corresponding openings on its face and sides. As the plug is pushed into the outlet, the flexible fingers enter the openings; the locking tabs are biased into the side openings to positively engage the plug and receptacle together.
Notwithstanding the wide variety of designs encompassed by the prior art, many presently-available locking connectors and adapters are relatively complex, correspondingly difficult and expensive to manufacture, and too delicate and breakage-prone for long-term household or industrial use. Some locking connectors require special tools to disengage and remove a locked plug. Others can be used only with specially-designed sockets or wall outlets; these cannot be used with standard, general service outlets of the types prescribed by the National Electrical Code (NEC) or the American National Standards Institute (ANSI).
There is a continuing need for locking electrical adapters and connectors which can be used to releasably secure a plug to a conventional extension cord socket, wall receptacle, or the like, including receptacles that meet NEC and ANSI standards. Such devices should be simple and easy to manufacture, aesthetically pleasing to consumers, easy to use, and further the safe and uninterrupted use of electrical appliances and tools that frequently require the dragging or hanging portions of the power cord (or extension cord) during use.